The purpose of this study is to test the hypothesis that alternate-day prednisone or daily fish oil supplements will retard or prevent decline in renal function in children, adolescents, and adults less than 40 years of age with moderate to severe IgAN. The primary outcome criterion will be a fall of 40% in estimated glomerular filtration rate, based on serial determinations of serum creatinine measured by HPLC. To date this site has four patients on study medications and one patient in the screening process. All of the patients are adults and doing fairly well. One of the patients has complaints of weight gain and moon face and we were able to reduce the study medication hoping to relieve these side effects for this patient. Nationally, there have been 74 patients randomized with 70 patients starting study medications. 8 patients have discontinued from the study for the following reasons: 2 with reduced GFR>40% from baseline, 4 lost to follow-up, 2 due to side effects which were heartburn and mood swings. Nationally, 20 patients have completed the 2 year medication regimen and are now on follow-up.